2013 HSC COURSE

make predictions based upon particular theoretical models of reality. The model is only considered to be valid (i.e. accurately describes reality) if the predictions made are experimentally varified.

einstein used thought experiments to investigate particular theoretical models of reality that could not be experimentally varified at the time due to limitations in technology

There is a train going at constan v with an obersver A inside the train and a stationary observer B outside the train. A flash of light is given off at the center of the traincar just as the two observers pass each other. The observer on board the train sees the front and back of the traincar at fixed distances from the source of light and as such, according to this observer, the light will reach the front and back of the traincar at the same time. The observer standing on the platform, on the other hand, sees the rear of the traincar moving (catching up) toward the point at which the flash was given off and the front of the traincar moving away from it. As the speed of light is finite and the same in all directions for all observers, the light headed for the back of the train will have less distance to cover than the light headed for the front. Thus, the flashes of light will strike the ends of the traincar at different times.

There is a train going at constant v c with an obersver A inside the train and a stationary observer B outside the train. Observer A holds up a mirror infront of him at arms length will the observer see his reflection. By the aether model no - since light can only travel at 3 x 10^8 and the trains velocity = c. This violates the principle of relativity. By the principle of relativity the observer A would see his reflection however observer B would see the light travel at 2xc. Einstein decided that the reflection would be seen due the the principle of relativity and that observer B would see the light travel at c meaning that space and time are relative and the aether model was superflous

1875 metre defines to be the distance between 2 lines inscribed onto a single bar of platium-iridium alloy. Current definition: i metre = length of the paths travelled by light in a vacuum during a time interval for ~3 millionths of a second. more precise and accessable using the advantage of c being constant and current technology's ability to measure time and c to great precision.

distance travelled by light in one year. light years = c x number of years

in order to be considered valid i.e. accurately describing reality a theory needs to be experimentally varified (provided evidence for)

the flying of atomic clocks to determine the existence of time dilation the dilated lifetimes of mesons penetrating the Earth’s atmosphere the energy yield from converted mass in nuclear reactions the observed increase in the mass of particles accelerated to near-light speed, in devices such as particle accelerators.

1st postulate: all laws of physics are thes time in all inertial frames of reference. 2nd postulate: the speed of light in empty space has the same value c in all inertia frames of reference. statement: the aether is superflous - no longer needed to explain the behaviour of light

relativity of simultaneity - 2 event judged to be simultaneous by 1 observer will not always be judged to be simultaneous by another, depends on the frame of reference. equivalance between mass and energy. Rest mass of an object is equivalant to a quantity of energy. Mass can be converted to energy and energy to mass E = mc^2. Time dialation, mass dialation and length contraction

g force = 0. in orbit the circular motion of the space craft means that the craft and the astronauts are accelerating towards earth at 9.8 (push pull cancels). Because the craft is accelerating at the same rate as it occupants there is no reaction force on the astronauts.

muons are formed when cosmic rays strike molecules in the outer atmosphere. They have a half life of 10^-15s. By classical physics this would suggest that the muons would not hit the ground however there is evidence of otherwise. This is because of the theory of relativity. From the earths frame of reference the time dialates and there for the 1/2 life is larger and from the muons frame of reference the length is contracted.

At the moment there is no implication as we dont have technology capable of reaching relativistic speeds where noticable mass dialations etc occurs. Provided relativistic speeds could be reached from the space crafts frame of reference space travel would be much shorter in distance and time than from the earths frame of reference. This would mean that much longer space missions to further away planets etc could occur. This would also much the cost of such would be much less due to the decreased fuel needed for the decreased distance. However there is a problem of mass dialation. As speed goes to c mass would dialate to infinity. By newtons second law F = ma, a = F/m. in order to deal with the mass dialations and still accellerate towards c a massive F would be needed which would greatly increase costs.

speak wisely what wise men do foolishly (Touchstone)

and fleet the time carelessly, as they did in the golden world. (Charles on duke seniors life in the forest refering to the golden age when all people lived in peace and innocence)

is the whetstone of the wits. (Celia is persuading Rosalind that the making of a dull witted person is not due to Fortune, but Nature — to the advantage of the witty, for they can use the dullard as a whetstone to sharpen their wits.)

— that was laid on with a trowel. (When Touchstone joins Rosalind in teasing LeBeau, Celia critiques their supposed witticisms as being rather overdone. (The trowel used to mortar brick walls is not a delicate instrument.))

O, how full of briars is this working-day world! (Celia has inquired if Rosalind's moodiness is due solely to her father's exile, and this is Rosalind's answer, in which she has has jumped over wooing and wedding and all that to the magical time when Orlando is the father of her child. For her, everything between the present time and that time is just a tangle of briars.)

many other mannish cowards have. That do outface it with their semblances. (Rosalind boasts to Celia that when she's dressed as a man and swaggers about, she'll look just as fearsome as men who look tough, but are really only "mannish."

Are not these woods More free from peril than the envious court? (Duke senior on the contrast of living between the court and the forest)

Finds tongues in trees, books in the running brooks, Sermons in stones and good in every thing.

Sweep on, you fat and greasy citizens . . .' (on the wounded stags herd ignoring the tearful situation)

Yea, providently caters for the sparrow, Be comfort to my age! (Giving Orlando all of his money, old Adam exclaims to Orlando that he will look to God for comfort in his old age, since God feeds both ravens and sparrows. (See Job 38:41 and Luke 12:6).)

Where none will sweat but for promotion (Orlando praises Adam as representative of the good old days, as contrasted with the present, when no one does anything except for reward or promotion.)

That ever love did make thee run into, Thou hast not loved (Silvius, the young shepherd, is advising an older shepherd in the ways of love. Silvius, full of the overweening assurance of youth, declares that if the older shepherd cannot remember every time he made a fool of himself for love, then he has not experienced true love.)

but as all is mortal in nature, so is all nature in love mortal in folly. (Touchstone is relating some of the follies he has committed in the name of love and concludes that love itself dictates mortal folly—silly acts which are bound to fail)

than thou art ware of. (Rosalind agrees with Touchstone's assessment of the folly of love. (She's probably thinking of her own crazy love for Orlando.))

till I break my shins against it. (Touchstone's repartee takes another meaning from Rosalind's "ware" (not 'aware,' but 'wary') when he replies that his wit will have to cripple him before it makes him wary.)

as a weasel sucks eggs. More, I prithee, more. (Jaques asks Amiens to continue his song even though Amiens has warned him that the song may make him melancholy. Jaques says he actually prizes melancholy, which he can find in almost any song as easily as a weasel sucks out the raw center of an egg.)

To blow on whom I please; for so fools have. — Duke Senior has jokingly promised Jaques that he can have a suit of motley, just like that of the fool Touchstone. Jaques now declares that he must also have freedom to criticize anyone about anything, as fools do.

The 'why' is plain as way to parish church:— Jaques continues his excited anticipation of foolery, declaring that the reason others must laugh at a fool in motely "is plain as way to parish church"; to take offense at what a fool says is foolish, so that even those his humor makes squirm will be

Presents more woeful pageants than the scene Wherein we play in. — After Orlando goes to fetch his aged friend, Duke Senior draws a moral from Orlando's story, and tells Jaques that they are not the only unfortunate people, that the world is a theatre which "presents more woeful pageants" than the scenes in which they personally participate.

And all the men and women merely players: They have their exits and their entrances;

Shall see thy virtue witness'd every where. Run, run, Orlando; carve on every tree The fair, the chaste and unexpressive she. — Orlando speaks to the absent Rosalind, telling her that "these trees shall be my books," as he intends to inscribe them with his love, by attaching poems to their bark. Orlando then tells himself what to do ("run, run Orlando"). He is so infatuated with Rosalind's beauty and virtue that words are useless ("unexpressive"); instead he must resort to putting poetry upon trees.